Nonwoven fabrics formed from polyethylene glycol modified polyester fibers and method for making the same

Abstract

Disclosed is a nonwoven fabric that is formed of polyethylene glycol modified copolyester staple fibers. The copolyester staple fibers include polyethylene terephthalate in amount sufficient for the copolyester staple fibers to possess dimensional stability properties substantially similar to those of conventional, unmodified polyethylene terephthalate fibers, polyethylene glycol in an amount sufficient for the copolyester staple fibers to possess wicking characteristics that are superior to those of conventional, unmodified polyethylene terephthalate fibers, and chain branching agent in an amount less than about 0.0014 mole-equivalent branches per mole of standardized polymer. Also disclosed are methods for making such nonwoven fabrics.

Description

[0001] This application is a continuation-in-part of pending application Ser. No. 09 / 484,822, filed Jan. 18, 2000, for Polyethylene Glycol Modified Polyester Fibers and Method for Making the Same, which itself is a continuation-in-part of pending application Ser. No. 09 / 444,192, filed Nov. 19, 1999, for a Method of Preparing Polyethylene Glycol Modified Polyester Filaments. Each of these pending applications is commonly assigned with this application and is hereby incorporated entirely herein by reference.[0002] The present invention relates to nonwoven fabrics having exceptional moisture management characteristics. The present invention also relates to the manufacture of such nonwoven fabrics from polyethylene glycol modified copolyester staple fibers.[0003] Disposable diapers and other personal care products formed of nonwoven, synthetic fabrics are extremely popular. In fact, disposable diapers made of such nonwoven fabrics have now essentially replaced cloth diapers in the marke...

AI Technical Summary

Benefits of technology

[0102] A particular advantage of the present invention is that the disclosed copolyester fibers may be dyed at atmospheric pressure without a carrier (i.e., a dye bath additive that promotes the dyeing of hydrophobic fibers), although leveling and dispersing agents are recommended. Moreover, unlike conventional polyester fibers, which typically require an acidic dye bath adjustment to a pH of about 4-5, the present copolyester fibers do not require any pH modification. In this regard, the copolyester can be effectively disperse dyed in an alkaline dye bath having a pH as high as 10, limited only by the stability of the disperse dyes at such alkaline conditions and 210.degree. F. rather than the properties of the present copolyester. Furthermore, the copolyester fibers of the present invention have comparable hand to polyester microfibers (i.e., fibers<1 dpf), yet demonstrate superior dyeing properties.

[0103] The nonwoven fabrics of the present invention can include PEG-modified copolyester fibers and cellulosic fibers (e.g., cotton fibers, rayon fibers, or acetate fibers) that can be dyed in one step. This is expected to reduce dyeing and energy expenditures by 30 percent or more. For example, cotton is typically dyed using cotton dyes (e.g., reactive dyes) in alkaline dye baths and polyester is typically dyed at high temperatures (e.g. 265.degree. F.) in acidic dye baths. Accordingly, dyeing blended cotton and polyester fabrics requires a two-step dyeing process. Such blends are usually dyed in an alkaline pH using suitable cotton dyes to selectively dye the cotton fibers and are thereafter dyed in an acidic pH using disperse dyes to selectively dye the polyester fibers. As described previously, however, the present copolyester fibers do not require any pH adjustment and can be dyed effectively in an alkaline dye bath having a pH as high as 10. Consequently, blended fabrics that are made from PEG-modified copolyester fibers and cotton fibers or other cellulosic fibers can be dyed simultaneously in an alkaline dye bath that includes both reactive and disperse dyes. Preferably, dyeing such cellulosic / copolyester blends is carried out in a dye bath having a pH of about 10 or less and a temperature at or below the boiling point of water at atmospheric pressure (i.e., 212.degree. F. or 100.degree. C.).

[0104] The copolyester fibers formed according to the present invention also possess a high exhaustion rate, which translates to reduced dye costs and fewer environmental issues. In fact, dye uptake is maximized near the normal boiling point of water (i.e., 212.degree. F.). In preferred embodiments, the dyeing of the copolyester fibers employs a relatively high ramp rate of about 5.degree. F. per minute below 100.degree. F., as the fibers absorb little dye at such temperatures. Above 100.degree. F., however, the fibers do absorb dye and so the ramp rate should be reduced to about 2.degree. F. per minute to achieve level dyeing. Optionally, a holding period between about 5 and 10 minutes may be employed between about 120.degree. F. and 190.degree. F. to promote level dyeing.

[0105] An effective ramp technique for batch dyeing, especially for jet or beck dyeing, is illustrated as FIG. 8. Minor adjustments to FIG. 8 may be appropriate for package and beam dyeings. Because the copolyester fibers of the present invention begin to dye at 100.degree. F., fabrics formed from the copolyester fibers should be home laundered in cold to warm water (i.e., less than 105.degree. F.) to ensure that dyes from other fabrics do not stain the copolyester fabrics.

[0106] To evaluate the dyeing characteristic, the disperse dyeability of the PEG-modified copolyester was studied using Color Index Disperse Blue 56, 73, and 79. See

Problems solved by technology

This increases the duration that a product can be used before disposal.

Such treatments, however, are typically inadequate to permit multiple uses, which the marketplace demands for diapers.

This reduces filament strength, which can lead to processing failures.

U.S. patent application Ser. No. 09 / 444,192 explains that branching agents promote cross-linking, which can lead to relatively weaker textiles.

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